In-situ observations of aerosol optical properties were conducted in Jinan, an urban site, from December 2013 to May 2014 and on Tuoji Island, a coastal site, from December 2014 to January 2015; both locations are located in Shandong Province, Northern China. Aerosol optical properties, such as the scattering coefficient (sigma(sp)), absorption coefficient (sigma(ap)) and single-scattering albedo (omega), were obtained using nephelometer and aethalometer. The mean values (+/- standard deviation) for sigma(sp) at 550 nm and sigma(ap) at 532 nm, were 204 +/- 188 Mm(-1) and 43 +/- 33 Mm(-1), respectively, in Jinan and 210 +/- 246 Mm(-1) and 8 +/- 6 Mm(-1) on Tuoji Island, respectively. The average omega at 532 nm was 0.80 +/- 0.09 in Jinan and 0.93 +/- 0.04 on Tuoji Island. Pronounced diurnal cycles were observed at both locations for sigma(sp), sigma(ap) and omega, but the diurnal cycles at the two locations exhibited distinct properties for some of the aerosol optical parameters. The values of sigma(sp) and sigma(ap) peaked between 0800 and 1100 local time (LT) due to traffic emissions and low wind speeds at both locations. And a unimodal omega diurnal cycle, which peaked between 1000 and 1400 LT, was observed in the spring in Jinan. This spring diumal pattrn was mainly related to secondary aerosol formation and aging processes. The high sigma(sp) and sigma(ap) values in Jinan winter were accompanied by calm winds (<2 m/s) from 0 degrees to 90 degrees, while the high sigma(sp) and sigma(ap) values on Tuoji Island were observed during the period of stronger wind speeds (>2 m/s) from 180 degrees to 270 degrees. This indicates that local emissions were a key source of strongly absorbing and scattering aerosols in Jinan during heating period, whereas, high sigma(sp) and sigma(ap) values on Tuoji Island were mainly influenced by middle- and long-distance transport from Shandong Province and the Jing-Jin-Ji region. Additionally, middle- and long-distance regional transport from direction at 180 degrees to 270 degrees occasionally enhanced the sigma(sp) and sigma(ap) values in the spring at Jinan after heating period. The sigma(sp) values in Jinan and Tuoji Island both exhibited relatively profound correlation with the accumulation mode particle number concentrations. (C) 2017 Elsevier B.V. All rights reserved.

Daytime and night-time PM1 and PM2.5 samples were simultaneously collected at the summit of Mount Tai during summer and autumn 2014. The mass concentrations and chemical compositions were analysed to determine the temporal variations of PM1 and PM2.5 and their contributions to visibility impairment. In summer, the average mass concentrations of PM1 and PM2.5 were 38.16 mu g/m(3) and 53.33 mu g/m(3), respectively. In autumn, the values were 42.75 mu g/m(3) and 59.16 mu g/m(3). Water-soluble inorganic ions were the most abundant species in both PM1 and PM2.5, followed by organic mass (OM). Among the major water-soluble ions, SO(4)(2-)and NH4+ had higher concentrations in summer than in autumn, whereas the concentration of NO3- showed the opposite seasonal trend. Lower concentrations of organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) were obtained in summer than in autumn. The water-soluble components (SOO42-, NO3-, NH4+ and WSOC) showed a clear diurnal variation due to the specific meteorological conditions of Mount Tai. The water content in PM1 and PM2.5 was enhanced by the water-soluble components, especially NH4NO3. The decreased visibility resulted from the combined influence of particulate matter and relative humidity (RH). The threshold PM2.5 concentration corresponding to a visibility of <10 km was 56.60 mu g/m(3), which decreased with an increase in RH. A revised IMPROVE equation was applied to estimate the light-extinction coefficient b(ext), which was found to be lower for these chemicals in autumn(364 Mm(-1)) than in summer (482 Mm(-1)). (NH4)(2)SO4 made the largest contribution to b(ext) in both summer and autumn, with an average rate of 56.97%. OM (17.32%) and NH4NO3 (15.13%) were also important contributors, with similar contribution rates. The contribution of NH4NO3 to bext was higher during summer, and OM contributions were higher during autumn. (C) 2016 Elsevier B.V. All rights reserved.